1. Field of the Invention
This invention relates to silacyclobutane functional siloxanes.
2. Background information
Silacyclobutane monomers are known and have been polymerized. To applicants' knowledge, however, stable silacyclobutane functional polyorganosiloxanes have not previously been made in high yield by a method which allows controlled design of the polymer structure. The polymers of the invention are useful intermediates for formulating room temperature vulcanizable and hot air vulcanizable silicone elastomers.
The preparation of silacyclobutanes of the formula ##STR3## where Y is chlorine or hydrogen, R' is hydrogen or methyl, and R is a monovalent hydrocarbon radical free of aliphatic unsaturation, and polymers derived therefrom, were revealed by Sommer in U.S. Pat. No. 3,046,291, issued July 24, 1962. Polymerization was accomplished upon heating or simply standing and optionally in the presence of a catalyst from the group consisting of alkaline materials such as NaOH, KOH, LiOH; quaternary ammonium compounds; and metallic salts of sodium, aluminum, iron, cobalt, manganese, lead and zinc.
Siloxane derivatives of silacycloalkanes of the formula ##STR4## where n is 3, 4, or 5, and R is methyl, phenyl, or chlorine, were reported by Nametkin, Vdovin, and Babich in Khim. Geterotsikl. Soedin, (Chemistry of Heterocyclic Compounds) (1966) (4) 630. They were obtained by hydrolysis or cohydrolysis of silacycloalkanes with alkylsilanes having OH, ONa, or OAc groups at the silicon atom.
Mixtures of siloxane derivatives of silacycloalkanes are prepared by this route and contain both desireable and undesirable species whose composition is dependent upon the reaction conditions employed. Preparation of siloxane derivatives of silacyclobutanes by a hydrolysis route is also undesirable as the silacyclobutane ring is known to react with water, thus opening the silacyclobutane ring and rendering it less reactive.
U.S. Pat. No. 3,398,178, issued Aug. 20, 1968 to Nelson, teaches how silacyclobutanes react with a catalytic amount of halogenated silane, hydrohalic acid or aluminum halide to polymerize by opening the ring to form a polymer consisting essentially of ##STR5##
In U.S. Pat. No. 3,445,495, issued May 20, 1969, Nelson teaches the formation of similar polymers by polymerizing silacyclobutanes in the presence of a platinum catalyst, and, optionally, a silane monomer containing an SiH bond.
Jonas and Owen show alkoxy and amino silacyclobutanes in U.S. Pat. No. 3,687,995, issued Aug. 29, 1972, which they say may be reacted with organosilicon materials containing SiOH groups and therefore may be useful as cross-linking agents. This use is claimed in U.S. Pat. No. 3,694,427. These compositions have the disadvantage of undergoing gradual increase in viscosity with time, requiring the components to be stored separately if spontaneous thickening is undesirable. Further, these formulations emit volatile condensation byproducts.